[mythtv-users] file size 'B'

[Michael T. Dean]

On 09/18/2009 10:07 PM, Jarom McDonald wrote:
> On Fri, Sep 18, 2009 at 7:57 PM, Fraser, Douglas wrote:
>>>> That sounds like you need to rescan your channels.  You may have "Use
>>>> quick tuning" enabled for "Live TV only", which would allow tuning to
>>>> succeed for LiveTV but not for recordings.
>> Thank-you for the tip about "Use Quick Tuning", it was set by default to
>> "LiveTV Only".  After I changed that field it started grabbing video again.
>>  This all worked fine for 3 weeks,  I shall have to dig around and try and
>> figure what could have changed.  Thanks again.
> In my experience, there are two reasons why you'd be experiencing these
> symptoms and seeing them fixed with the "Use Quick Tuning" setting:
>
> 1) There is a signal problem. This past summer my cable company was playing
> with signal strength for some of their clear QAM channels but not others,
> and hence I'd have patterns of 0-B recordings on particular channels. I
> reported this to them and and they brought me a professional grade
> amplifier.
>
> 2) The channels have actually been moved by the cable company. This can be
> related to the previous problem, as I've noticed that when cable companies
> move channels around, often they still send the signal out for a while on
> the older frequencies but at a much lower fidelity, or they use certain data
> to help certain kinds of tuners find the new frequencies. "Quick tuning"
> gets a lock directly through the device rather than involving MythTV in the
> process (I think ... smarter people than I could explain it better) and so
> can often pick up channels when they've moved. However, to future-proof your
> setup you really should re-scan your channels through mythtv-setup as Mike
> suggested, so that if they have moved then MythTV will have the most current
> frequency info. "Quick Tuning" is a useful feature but can mask some
> problems like this that will have to be addressed.

Yeah, AIUI, quick tuning basically uses the serviceid we found last time 
we successfully tuned the channel to tune the channel rather than 
actually reading the tables to find out how the 
broadcaster/rebroadcaster is saying to tune the channel now.  It's a 
"sloppy" tune that's not very reliable, but that can be faster than a 
proper tune--assuming nothing has changed.  Since tuning without quick 
tune is not working, that means something has changed (and you may well 
be in that "interim" period Jarom mentioned).

So, the best approach is to rescan and fix your channels rather than 
ignoring the symptom and pretending all is good.  :)

Mike